Thiazolidones as light stabilizers for plastic compositions



ii a c acme Elli C 1 r3 g l Patented July 9, 1963 l. 2 3 997 1% Ageneral formula for the compounds which are oper- THEAZQHDQNES LHEHTSTABHJEZERS F63 ative in our invention has the following configuration:

PLASTIC CGMPOSHKGNS RNC=O Gerald R. Lappin and John W. Tamblyn,Kingsport, l J X Tenn, and James A. Van Allan, Rochester, N.Y., as- 5signers to Eastman Kodak Company, Rochester, NFL, 3 O a corporation ofNew Hersey N0 Drawifig- Filed 195g, 4,174 The range of derivatives isillustrated as follows in Table 6 Claimswfipl'ml I and shows theappropriate structure for R, R and X. This invention relates to lightstabilizers for plastic 10 The ultraviolet absorption data Were Obtained011 methcompositions, more particularly plastic compositions such anolsolutions of the compounds.

TABLE I Chemical analysis Wavelength at maximum Molar R R X Cale. Obs.absorption, extinction Mmp) coefficient,

000- Percent Percent Percent Percent 0 1-1 '0- H c n. 06m H 330 2.6 CGH5C611 H 330 2.0 I1-C6H13 CGHS 2-0 0H3... 68.1 7.0 68.3 6.9 355 2.3 n-CHzs C6115 H 75.8 9.7 75.7 8.9 330 2.88

CH3 CH3 /CH3 O 24-o 76.0 6.1 75.9 6.0 339 3.0

as polyesters. In our preferred embodiment of this invention, a t-hiMany organic plastic compositions undergo deterioraazolidone representedby the following general structural tion of one sort or another whenexposed to sunlight due formula is used: to the action of ultravioletlight. Conventional stabi- 0:0 lizers such as phenyl salicylate, protectsome plastics l quite effectively against damage from radiation wavelengths below about 3400 A. Certain benzothiazole and X S Ybenzothiazoline derivatives behave much like phenyl salicylate in thisrespect. However, radiation of longer wave lengths is not withoutharmful eiiects on many plastics and there has been a need forprotection over a wider range.

One object of this invention is to provide a light stabilizer forplastic compositions which gives improved pr0tection in the nearultraviolet range. A further object of this invention is to provide anultraviolet stabilizer which has good compatibility and givessubstantial protection against ultraviolet radiation to polyesters. Afurther object of this invention is to provide an ultraviolet inhibitorwhich is free from color change when incorporated into plasticmaterials.

We have found that certain derivatives of 4-thiazolidone absorb stronglyin the near ultraviolet and also give surprisingly good protectionagainst ultraviolet damage where X and Y are selected from the classconsisting of alkyl groups containing one to twelve carbon atoms, alkoxygroups containing one to twelve carbon atoms, halogen, or a nitro groupand R is selected from the class consisting of alkyl groups containingtwo to twelve carbon atoms and aryl groups substituted with groupsselected from the same class as X and Y. Approximately 5% based on theweight of the plastic material of the inhibitor is incorporated into theplastic. These thiazolidones are relatively heat stable and have theadvantage that they can be incorporated into a molten polyester withvery little increase in color, whereas certain other ultravioletinhibitors result in considerable coloration under similar treatment.

The following examples are intended for illustration of our inventionbut are not intended to limit it in any when incorporated in plastics.These thiazolidones are Way:

Example 1 prepared by refluxing equimolecular amounts of the thiourea,ethyl chloroacetate, and pyridine in alcohol for P 0f -tmisyl-Z-misylimin0 5-anisyZidene-4- 3 to 5 hours as follows: thiaz0lid0ne.-Am1xture of 61 1g. (0.5 mole) of p-anisi- ClOHaCOOCZHS dine, 57 g. (0.75mole) of carbon dlSlllfidfi, and 10 g. of

powdered potassium hydroxide was refluxed 6 hours.

| O=NR 65 After cooling the mixture was acidified with 6 N hydroschloric acid, filtered, washed with water and methanol, Thisthiazolidone is condensed with an aromatic aldedried a vacuum Oven ThereP hyde using piperidina as a catalyst as follows: tamed 68 g. (95%) of4,4 -dlmethoxythiocarbamlide,

melting point 187189 C.

A mixture of 28.8 g. (0.1 mole) of the above product,

R' =o\ /CH2 R'N=O\ /o=11o-R" 24 g. (0.2 mole) of ethyl chloroacetate, 17m1. of pyri- S S dine, and 500 ml. of ethanol was refluxed 20 hours.

After cooling the mixture was diluted with 1 liter of water Example 2Preparation of 3-anisyl-Z-anisylimino-S-benzylidene-4- thiazlid0ne.-Amixture of 10 g. (0.03 mole) of 3-anisyl- 2-anisylimino-4-thiazolidone,prepared as in Example 1, 3.5 g. (0.03 mole) of benzaldehyde, 100 ml. ofethanol, and ml. of piperidine was refluxed for 4 hours. After coolingthe mixture was diluted with 25 ml. of water and filtered. The productwas recrystallized from ethanol to give g. (80%) of3-anisyl-2-anisylimino-S-benzylidene- 4-thi'azolidone, melting point174l75 C.

Example 3 Preparation ofS-benzylidene-S-hexadecyZ-Z-phenylimino-4-thz'az0lidone.86.8 g. (0.36mole) of hexadecylamine was dissolved in 300 ml. of hexane at 70. Thesolution was stirred and to it was added dropwise 46.4 g. (0.36 mole) ofphenyl isothiocyanate. After cooling the mixture was filtered and theproduct air-dried. There was obtained 117 g. (88%) ofN-hexadecyl-N'-pheny1- thiourea, melting point 8081 C.

A mixture of 116 g. (0.31 mole) of the above product, 42 g. (0.34 mole)of ethyl chloroaoetate, 31 g. (0.35 mole) of pyridine, and 350 ml. ofethanol was refluxed 18 'hours. After cooling, the mixture was dilutedwith 100 ml. of water and filtered. The product was air-dried to give120 g. (95%) of 3-hexadecyl-2-phenylimino-4- thiazolidone, melting point53-55 C.

A mixture of 120 g. (0.29 mole) of the above product, 38 g. (0.33 mole)of benzaldehyde, 30 g. (0.35 mole) of piperidine, and 600 ml. ofmethanol was refluxed 18 hours. The mixture was cooled and filtered. Theprodnot was recrystallized from acetone to give 124 g. (85%) of5-benzy1idene-3-liexadecyl-2-phenylimino-4 thiazolidone, melting point7274 C.

Example 4 Preparation ofZ-phenylimino-S-plzenyl-5-cumal-4-thiazolidona-A mixture of 99 g. ofthiocarbanilide and 68 g. of ethyl chloroacetate is heated to 110; thereaction mixture becomes fluid in about 10 min. and there is a vigorousevolution of ethyl alcohol. The mixture quickly solidifies to a whitecrystalline mass. (This is a hydrochloride which melts at 207210.) It iswarmed on the steam bath for one hour to complete the reaction. Thecrude reaction mixture is broken up, washed with benzene, and filtered.It is then stirred with sodium bicarbonate solution for one hour,filtered, and dried.

(The sodium bicarbonate solution liberates the free base.) The yield of2-phenylimino-3-phenyl-4athiazolidone is 101 g. (86%), melting point168171 C. It may be recrystallized from butanol, after which its meltingpoint is 176 C.

A mixture of 26.4 g. (0.1 mole) of 2-phenylimino-3-phenyl-4-thiazolidone and 16 g. (16.5 ml.) (0.1 mole) ofisopropylbenzaldehyde in 160 ml. of methanol was brought to vigorousreflux on the steam bath. Piperidine (10 ml. in 15 m1. of methanol) wasadded. (Although piperidine is a catalyst, the amount used in largerreactions should be increased proportionately.) The fluid phase of thereaction mixture became lemon yellow, and some of the2-phenylimino-3-phenyl-4athiazolidone dissolved, but a clear solutionwas never obtained. (In a run using 16 g. of the thiazolidone, 15 m1. ofisopropylbenzaldehyde and 10 ml. of piperidine complete solution wasobtained for about 5 min. The reaction mixture set to a crystallinemass.) The yield in this case was 93% (crude). Reflux was continued fortwo hours. The reaction mixture was then chilled, and the product wasfiltered ofl, washed with methanol, and dried. The yield was 34 g., 87%;melting point, 172175 C. This was dissolved in 50 ml. of warmchloroform, and 200 ml. of methanol was added. After cooling to roomtemperature, the product was filtered and again washed with methanol.Pure white crystals resulted. The yield was 30 g., 75%; melting point178 C.

The stabilizers were tested by melt-compounding into the plasticcomposition and formed into flat sheets. In the case of celluloseacetate butyrate, one part of the stabilizer was rolled into the plasticwith 12 parts dibutyl sebacate. 50-mil thick sheets were then molded at320 F. and exposed in a modified Atlas Twin-Arc Weather- Ometer (Anal.Chem, 25, 460 (1953)). In the case of polyester made from 4,4-sulfonyldibenzoic acid and 1,5-pentanediol, 3 parts of the stabilizer were mixedwith the powdered polymer, extruded at 575 F. in the form of sheet30-mil thick and exposed as above.

The plastic samples, before and after exposure were tested for stillnessin flexure by the Tour-Marshall procedure (A.S.T.M. D747-43).Brittleness was defined to have developed in the exposed samples if theybroke at a bend angle of less than in this test. Stabilization ratingswere defined as. follows:

(1) Rating based on retardation of loss in flexural strength is theratio of exposure time required to cause 25% loss of original flexuralstrength in the stabilized sample to the exposure time for equal loss inthe unstabilized sample.

(2) Rating based on retardation of embrittlement is the ratio ofexposure time for development of brittleness in the stabilized sample tothe exposure time for develop: ment of brittleness in the unstabilizedsample.

Some tests were also made on a more rubbery type of polyester made froman equimolar mixture of 4,4-sulfonyl dibenzoic acid and azelaic acid,polyesterified with 1,5-pentanediol. This polymer was dissolved, with 5parts of the stabilizer to be tested, in tetrachloroethane and cast asfilms about 3-mil in thickness. These films were exposed in theWeather-Ometer as above until they broke when given one hard crease, theexposed side of the film being on the outside of the crease. This wastaken to be a semiquantitative standard state of brittleness. Thestabilization rating for the stabilizer was then defined to be the ratioof the exposure time for development of brittleness in the stabilizedfilm to the time for development of similar brittleness in theunstabilized film.

The thi azolidones were found to have an important advantage over manyother organic light stabilizers in that they have a higher inherent heatstability. For example, they can be safely heated in aromatic sulfonepolyesters at the high temperatures (about 300 C.) required in variousmelt-processing operations, such as polyesterification, film extruding,injection-molding, and fiber spinning.

Example 5 Table II gives stabilization ratings for several thiazolidonederivatives and cellulose acetate butyrate plastic sheets (13% acetyl,38% butwyl). For the unstabilized plastic, the exposure time required tocause either embrittlement or 25% loss of fiexural strength was about300 hours in the modified Weather-Ometer.

Phenyl salicylate, a standard light stabilizer for cellulose esters hasbeen included in Table II for comparison. In addition to thethiazolidones, three other thiazole derivatives approximately equivalentto phenyl salicylate in stabilizing activity have also been included. Atthe selected concentration of 1%, certain of these thiazolidones areshown to provide substantially improved protection over that obtainablewith phenyl salicylate or equivalent stabilizers.

TABLE II Stabilization rating based on retardation of- StabilizerFlexura-l Emhritstrength tlenient loss None 1 1 Phenyl salieylate 5 52-phenylimino-3phenyl thiazolidinc. 4 4 2-(Nethyl-rn-toluidiuo)benzothiazol 4 4 2-phenylimino-3-ethyl beuzothiazoline 5 52-phenylimin0-3phenyl-4-thiazolidone 3 22-phenylimino-3-phenyl-'-fural-4-thiazolidone 5 5 2 phenetylimino 3phenetyl 5 benzal 4 thiazolid nn 6 6 2-phenylimino-3-phenyl-5-cumnPl-thiazolidonel l 7 6 2 (p tolylirnino) 3 (p -tolyl) 5 ournalthiazolidone- 9 8 2 tolylimino) 3 (0 -tolyl) cumal 4 thiw-nlidn w 12 112 (o tolylimino) 3 (o tolyl) 5 benzal 4 thiazolidone 15 5 Example 6 Thesuperiority of the thiazolidones over the salicylate type of stabilizerswas even more pronounced in the case of the pent-amethylene4,4'-sulfonyl dibenzoate polymer, as shown in Table III. Exposure timerequired for 25% loss of flexural strength in the case :of theunstabilized plastic was about 300 hours in the modified Weather-Ometer.Brittleness developed in this material in about 200 hours. The threethiazole derivatives, included in Example 1 with phenyl salicylate werealso tested in the sulfone polyester and are included with Table III. Itmay be noted that these compounds not only failed to give any protectionbut actually accelerated ultraviolet breakdown of the plastic. This isshown by the fractional values for the stabilization ratings.

Example 7 The well known light stabilizer, 2-hydroxy-4,4'-dimethoxybenzophenone, was incorporated With the sulfone polyester of Example 2,before the polyesterification state. The polymer was then formed in thepresence of the stabilizer and the product extruded in the form of 30-mil thick film in the same Way as the test samples of Example 2.Considerable discoloration of stabilizer took place during these heattreatments. Stabilization ratings on this film were 1.0 and 0.9respectively for flexural strength loss and embrittlement. A filmsimilarly prepared containing2-phenylimino-3-phenyl-5-cumal-4-thiazolidone, on the other hand, showedno discoloration and gave stabilization ratings of greater than 14.

This ability of the thiazolidones to withstand high proc' cessingtemperatures without color deterioration or loss of stabilizing activityis highly advantageous. The stabilizing activity of any stabilizer isimproved with increased intimacy of dispersion. The latter can beattained best by incorporating the stabilizer before polymerization.This procedure usually involves considerably more exposure of thestabilizer to high temperatures.

Example 8 Thin films of the more rubbery sulfone polyester, describedabove, were =also well stabilized by addition of thiazolidones, as shownby Table IV. Several of the salicylate types of stabilizer and also2-phenylirnino-3- phenyl thiazolidirie, are included for comparison. Itmay easily be seen how much superior is the performance of many of thethiazolidones. In these tests the unstabilized film became brittle afterabout 40 hours exposure in the modified Weather-Orneter.

TABLE IV Stabilizer: fiifffi i None 1.0 Phenyl salicylate 1 Resorcinolmonobenzoate 2 Resorcinol monosalicylate 3 2-phenylimino-3-phenylthiazolidine l Z-amino thiazoline 1 2-butylimino-3-butyl-4-thiazolidone1 2-phenylirnino-3-butyl-4-thiazolidone 32-phenylimino-3-phenyl-4-thiazolidone 32-phenylirnino-5-benzal-4-thiazolidone 6 2 phenylimino 3 phenyl 5 benzal4 thiazolidone 8 2 phenylimino 3 phenyl 5 anisal 4 thiazolidone 102-phenylirnino-3ethyl-5-benzal-4-thiazolidone 11 2 0 ethylphenylirnino 3o ethylphenyl 5- benzal-4-thiazolidone 11 2 phenylimino 3 hexyl 5 (omethoxybenzal)-4-thiazolidone ll 2- (p-tert-butyl phenoxyphenylimino)-3-(p-tertbutyl phenoxyphenyl) 5 benzal 4 thiazolidone 11 2(o rtolylimino) 3 (o tolyl) 5 benzal- 4-thiazolidone 19 2 phenylimino 3phenyl 5 (p nitrobenzal)-4-thiazolidone 222-anisylimino-3-anisyl-S-benzal-4-thiazolidone 242-anisylimino-3-anisyl-5-anisal-4-thiazolidone 24 1 Based on retarditionof embrittlenient.

Example 9 Two of the films listed in Table IV of Example 8 were exposedoutdoors in Kingsport, Tennessee, for two clear days in September 1954.These films were the unstabilized control and the film stabilized with2-oatolylimino- 3-o-tolyl-5-benzal-4athiazolidone. The deterioration dueto weathering was evaluated for both films by measurement of theirinherent viscosity before and after exposure. The loss of inherentviscosity was found to be, respectively, 40% and 0.9%. inherentviscosity for both films before exposure was about 0.95.

In general, for this material, loss of inherent viscosity on weatheringwas found to run parallel with development of brittleness. Samplesusually became brittle when the viscosity loss was about 40%. Accordingto this measure, the thiazolidone-stabilized film was some 40 times asWeather-resistant as the unstabilized control.

The inherent viscosities were measured at 25 C. on solutions of thepolyester samples in a 60:40 (by weight) mixture of phenol andtetrachloroethane, containing 0.25

g. of the polyester per 100 cc. of the solvent. The inherent viscositywas defined to be In Nr where Nr, the relative viscosity, is the ratioof viscosity of the solution to viscosity of the solvent and c is 0.25.

Example 10 TABLE V Coneentra- Exposure tion of time for Stabilizerstabilizer 25% loss of (percent) tenacity (hours) None 4.5

2-phenylimino-3-phenyl-4-thiazolidone 22-phenylirnino-3-butyl-5-benzal-4-thiazolidone 22-phenylimino-3-butyl-5-benzal-4-thiazolidone 54 2-(o-ethylphenylimino)-3-(o-etl1yl phenyl)-5- 2 benzal--thiazolidone 2-(o-ethylphenylimino)-S-(o-ethyl phenyl)-5- benzal-ithiazolidone 5 192-Anisy1imino-3-anisyl-5-b enzall-thiazolidone 4 16Z-phenylimino-Ii-hexadeeyl-l-thiazolidone 4 ll2-phenylimino-3-hexadeey1-5-benza1-4-thiazoli- 2 14 It is evident thatplastic shapes even as thin as yarn filaments can be given a substantialdegree of protection against damage from ultraviolet light.

Example 1 The thiazolidones can be applied to the yarn after spinning,for example, from a dye-bath. A sample of fabric Woven from theunst-abilized yarn of Example was immersed in a water bath at 90 C.2-phenylimino- 3-p-henyl-5-oumal-4-thiazolidone was dispersed in thebath to the extent of 2% based on the fabric weight. Sodium ligninsulfonate and Igepon T Were used as dispersing and wetting aids. Thefabric was. then washed, dried, and exposed in a Fade-Ometer until itlost 25 of its original tenacity. A control sample of the unstabi-lizedfabric was similarly treated but with the thiazolidone omitted from thewater bath. This fabric lost 25% of its original tenacity after 26 hoursin the Fade-Ometer while the stabilized fabric required 65 hours toreach the same stage of deterioration.

Example 12 Table VI gives the results of stabilizing polypropylene with5-benzal-3-hexadecyl-Z-phenylimino-4-thiazolidone.

TABLE VI Percent Percent Exposure Exposure initial initial time timeConen. flexural inherent required required Stabilizer of stabistrengthviscosity to crack to break lizer (perleft left on crease on crease centby after 450 after 95 (hr.) (11!) weight) hours hours exposure exposureNone 0 23 75 150 5 -benzal -3 -hexadeeyl -2 phenylimino -4-thiazolidone1 70 70 250 450 Weathering exposures were made in an Atlas Twin-ArcWeather-Ometer modified by the addition of fluorescent sun lamps asdescribed in Analytical Chemistry, vol. 25, 4 60' (1953).

Example 13 The effectiveness of derivatives of 4-thiazolid0ne insuppressing the photo-oxidation of polyethylene is indicated from TableVI'I. was 1% by weight. Plates inch thick were exposed outdoors from Mayto September. Carbonyl contents of these plates were measured before andafter exposure and the carbonyl formed by photo-oxidation, obtained bydifference is expressed in arbitrary units.

TABLE VII Carbonyl formation otabihzer. (arbitrary units) None 55 3phenyl 2 phenylimino-S-(m undecylcarbamoyloxy)benzal-4 thiazolidone 65-ibenzal-3-eetyI-Z-phenylimino-4-thiazolidone 4 Example 14 TABLE VIIIStresscracking resistance, exposure time (days) required to crackStabilizer 1 5 10 sample samples samples None 330fi-(p-methoxybenzal)-8-(p-methoxyphenyl)-2-(p-methoxyphenylimino)-4-thiazolidone 395 400 4103-phenyl-2-phenylimino-5-(m-undeeylearbamoyloxy)benzali-thiazolidone 445460 470 5-benzal-3-eetyl-Z-phenylimino-l-thiazolidone. 1, 150 1, 176 1,261 3-hexyl-54o-methoxyben zal-2-phenylirnino-4- thlazolidone 741 765 1,113

As shown in Table VIII, two of the thiazolidones prevented cracking inall ten specimens of stressed polyethylene for over 2 years.

Example 15 A polyester made from a mixture or" 0.83 mole terephthalateacid, 0.17 mole of isophthalic acid and 1.0 mole ofl,4-cyclohexanedimethanol was extruded at 300 C. into a film 10 mil.thick. Samples of this film were exposed in the modified AtlasWeather-Ometer described above, and the progress of weathering damagewas followed by determining inherent viscosity as described in Example9. After 850 hours of exposure, this film lost 33% of its originalviscosity. The same polyester, which was mixed with 1% of3-hexadecyl-Z-phenylimino-S- benzal-4thiazolidone, extruded and exposedin the same way, showed a viscosity loss of 16%. Substitution of3-anisal-2-anisylimino-S-benzal-4-thiazolidone for the thiazolidonenamed above gave a film which lost only The concentration of stabilizer10% of its original viscosity after the same Weather- Ometer exposure.

The control film became dull on the surface after 400 hours exposure andbrittle after 1400 hours exposure. The film containing 1% of3-anisy1-2-anicylimino-5- benzal-4-thiazolidone was still not brittleafter 4500 hours exposure. It retained a glossy surface up to 1600 hoursexposure.

Example 16 Injection-molded tensile bars, ,1 inch thick, were preparedfrom a polyester made from a mixture of 30 mole percent terephthalicacid, 20 mole percent succinic acid, and 50 mole percentl,4-cyclohexanedimethanol. When these specimens were exposed in themodified Atlas Weather-Ometer they became brittle in 600 hours. Similarspecimens containing 1% of 5benzal-3-(2-ethylphenyl)-2-(2-ethylphenylimino) -4-thiazolidone werestill not brittle after 4700 hours. A similar improvement in theweathering resistance of a composition pigmented with 6% of a fineparticle-size calcium carbonate (Multiiiex MM) was obtained by theaddition of 1% of the above thiazolidone.

Example 17 Compression-molded sheets of poly(vinyl chloride), SO-milltln'ck, plasticized with 30 pts. dioctyl phthal-ate were exposedoutdoors. They darkened in color to a light brown in 2 months and to adark brown with dulled surface in 3 months. Surface cracks developed in1 year. Similar sheets containing in addition 4 pts, of an epoxystabilizer, hydroquinonebisglycidyl ether, also darkened in color onexposure but more slowly than the unstabilized composition. Theyretained a smooth glossy surface for 1 year. By 15 months whitishstreaks had developed on the surface. A third composition stabilizedwith 2 pts. of hydroquinonebisglycidyl ether and 2 pts. of2-anisylimino-3-anisyl-5-p(ii-hydroxyethoxy) benzal-4-thiazolidone wasalso exposed in the same way and at the same time as the first twocompositions. The original yellow color of this third compositiondarkened only slightly during exposure and is still only a yellow colorafter 2 years exposure. It retained a 'shiny surface for over a year.

Example 18 Low density (0.918) polyethylene was compressionmolded toplates inch thick which were cut into test specimens 1 /2 x /2 inch. Tenof these specimens were bent into a U-shape and exposed outdoors underthe stress required to retain them in this shape. The exposure timerequired to start cracks in half of these bent specimens (stress-cracklife) was recorded. Similar exposures were made on polyethylenecompositions containing 1% of various 4-thiazolid0ne derivatives. TableIX gives the results. It is apparent that a substituent in theS-pcsition on the thiazol-idone molecule is necessary [forstabilization. For good stabilization an aromatic substituent in the5-position appears to be necessary, although insufficient.

Retention of elongation after 1 years outdoor exposure of who abovepolyethylene compositions in 50-mi1 thick compression-molded sheets, cutinto tensile specimens, is also shown in Table IX. The results run moreor less parallel with the stress cracking resistance. The resistance ofthe same sheets to photo-oxidation in terms of carbonyl formation after3 months outdoor exposure is given in the last column of Table IX. Thecarbonyl contents of the samples, before and after exposure, weremeasured by means of infrared absorption at 5.82 s. The changes incarbonyl content during exposure are somewhat less informative than thechanges in the mechanical properties because the carbonyl contents ofthe thiazolidones themselves vary and are not always completelyseparable from the carbonyl developed in the polyethylene byphoto-oxidation.

TABLE 1X STABILIZATION OF POLYETHYLENE WITH DERIVATIVES OF 4-THIAZOLIDONE Initial Carbonyl Stresselongation forma- 4-thiaz01idone added (1%)crack retained tion: arbilife, after 12 mo. trary mos. exposure, unitspercent None (unstabilized control) 12 16 372-phenylimino-3phenyl-5-(3-n-octyloxy) benzal 24 0 2-phenylimino-3-phentoxy)-benzal 24 99 0 2-phenylimino-3-cetyl-5-(2carb0- methoxy)-benzal 2405 6 2-phenylirnino-3-n-decyl-5-benzal 24 92 I O2-phenylimino-3-n-hexyl-5-(2-methoxy)- benzal 24 96 1 2-(l-tort-butylphenoxyphenylimino)-3- (4-tert-butylphenoxyphenyl)-5-benzal24 99 0 2-phenylirnino-3-(2,4-di-tert-amy1-phenoxy-phenyl-S-carbomethoxy) benzal 24 95 82,phenylimino-3-cetyl-5-(a-rnethoxy) benzal 24 96 42-keto-3-cetyl-5-benza1. 24 97 12-phenylimino-3-phenylamyloxybenzoxy-benzal 24 86 02-(2-ethylphenylimino)-3-(2-ethylphenyl)-5-(4-n-d0decyl)benzal 20 64 0 2cumylimino-3curnyl-5-(2-carbobutoxy)-benzal 18 93 02-(B-phenetylirnino)-3-(3-phenetyl benzal. 16 38 02'ethylirnino-3-ethy1-5-(2-thienyl) 16 33 202-phenylimino-3-phenyl-5-(4-nitro) benzal 16 68 92-pheny1irnino-3-phenyl-5-fural.,. 15 33 102p-toly1imino-3-t0lyl-5-cumal 15 51 1 2butylirnino-3-butyl 12 12 17Example 19 A similar set of data for polypropylene is shown in Table X.Films 3-mil thick were cast from Tetralin dopes. A concentration of 5%was used for each thiazolidone tested. The density of the polypropylenewas 0.915 and its inherent viscosity at 0.25% concentration in Tetralinat C. was 1.53. The exposure times in the modified Weather-Ometerrequired to cause crease embrittlement in these films were recorded. Thestabilization ratings list-ed in Table X are the ratios ofembrittlernent time for the stabilized film to embrittlement time forthe unstabilized control film. The latter became brittle in about 25hours.

TABLE X 4-thiazol-idone added 5% stag None (unstabilized control) 1.05-benzal-3-hexadecyl-2-phenylimino 7.83-ethyl-S-(o-methoxybenzal)-2-phenylimino 7.8 S-(m-hydro-xybenzal)-3-phenyl-2-phenylimino 7.5 S-benzal-3-butyl-2-phenyl-imino 6.73-phenyl-2-phenylimino 3.9 5benzal-2-phenylimino 3.53-ethyl-2-ethylirnino-5-(Z-thienyl) 1.7

Example 20 The subject stabilize-rs were incorporated at 1% in an alkydpolyester prepared from 0.2 mole of phthalic anhydrzide, 0.2 mole maleicanhydride, 0.4 mole of propyleneglycol and 0.3 mole of styrene. Testpieces were pressed in the form of in.-thick plates and exposed in theWeather-Ometer for 1000 hours. Yellowing was determined by opticaldensity measurement at a Wave length of 450 Ill 1.. Table XI presentsthe data obtained.

1 1 TABLE x1 STABILIZATION OF AN ALKYD POLYESTER RESIN WITH DERIVATIVESOF i-THIAZOLIDONE 4-thiazolidone added 1%); (1232 53 None (unstabilizedcontrol) 0.40

2 phenylimino 3 phenyl benzal 4- A polyester made from 1 mole ofterephthalic acid and 1 mole of ethyleneglycol was extruded at 270 C.,drafted 200% at 105 C. in each of two mutually perpendicular directionsand heatset at 200 C. for 30 sec. to produce .a crystalline film 3 milsthick. When exposed in the modified Weather-Ometer for 300 hours thisfilm lost 60% of its initial elongation. A similar polyester wasprepared with the addition of 1% of 2(o-toly limino)-3-(o-tolyl)-5-benzal-4-thiazolidone and was extruded, processed andexposed in the same way as the unstabilized film. This film lost only ofits initial elongation during the Weather-Ornete-r exposure.

Example 22 I A polyester made from 1 mole of phosgene and 1 mole of thesodium phenolate of 2,2-bis(p hydroxyphenyD- propane was cast in theform of l-mil thick film from a methylene chloride dope. This film lost75% of its initial elongation after 300 hours exposure in the modifiedWeather-Ometer. To a sample of the same dope was added 1% of2-anisylimino-3-anisyl-5-anisylidene- 4 thiazolidone, based on thepolyester content of the dope, and a similar film cast after thoroughmixing of the dope. This film lost only of its initial elongation afterthe same exposure.

Certain derivatives of 4-t-hiazolidone are specifically useful as lightstabilizers because of their low volatility and low solubility. Lossesfrom thin plastic shapes, such as fibers and films, are thus minimized.The low color of these stabilizers, usually in the pale yellow range,and freedom from color change on exposure to 'light is a furtheradvantage. Their remarkably good heat stability makes it possible tosubject them to high temperature fabricating processes which are out ofthe question for many organic stabilizers.

These thiazolidones may be used With many kinds of plastics to improvethe light stability such as cellulose esters, polyesters, polystyrene,vinyls, polyethylene, and the like.

Unless otherwise indicated the temperatures given herein are centigrade.

This is a. continuation-in-part of application Serial No. 637,100, filedJanuary 30, 1957, now abandoned.

We claim:

1. A molded article essentially consisting of cellulose acetate butyrateand 15%, based on the weight of the cellulose acetate butyrate, of athiazolidone having 'the formula:

X S Y Where X and Y are each selected from the group consisting of alkylradicals containing one to twelve carbon atoms, alkoxy radicalscontaining one to twelve carbon atoms, halogen and nit-ro and R isselected fromthe group consisting of alkyl radicals containing two totwelve carbon atoms and aryl radicals substituted with substituentsselected fromthe same group as X and Y.

2. A molded article essentially consisting of cellulose acetate butyrateand 1-5%, based on the weight of the cellulose acetate butyrate, of athiazolidone having the formula:

Where X is selected from the group consisting of alkyl radicalscontaining one to twelve canbon atoms, alkoxy radicals containing one totwelve carbon atoms, halogen and nitro and R is selected from the groupconsisting of alkyl radicals containing two to twelve carbon atoms.

3. A molded article essentially consisting of cellulose acetate butyrateand 15% based on the weight of the cellulose acetate butyrate, of athiazolidone having the formula:

where R is selected from the group consisting of alkyl radicalscontaining two to twelve carbon atoms and X and Y are each selected fromthe group consisting of alkyl radicals having one to twelve carbonatoms, halogen and nitro and R is selected from the group consisting ofalkyl radicals containing two to twelve carbon atoms and aryl radicalssubstituted with substituents selected from the same group as X and Y.

4. A molded article essentially consisting of cellulose acetate butyrateand about 1%, based on the Weight of the cllulose acetate butyrate, of2-phenylimino-3-phenyl- S-benzal 4-thiazolid0ne.

5. A molded article essentially consisting of cellulose acetate butyrateand about 1%, based on the Weight of the cellulose acetate butyrate, of2,4-diketo-5(4'-butoxybenzal) 4-thiazolidone.

6. A molded article essentially consisting of cellulose acetate butyrateand about 1%, based on the Weight of the cellulose acetate butyrate, of5-(4-isopropylbenzal)- 2,4-diketo 4-thiazolidone.

References Cited in the file of this patent UNITED STATES PATENTS2,680,727 Jarboe June 8, 1954 2,739,888 Sawdey Mar. 27, 1956 2,739,971Sawdey Mar. 27, 1956 2,808,330 Sawdey Oct. 1, 1957

1. A MOLDED ARTICLE ESSENTIALLY CONSISTING OF CELLULOSE ACETATE BUTYRATEAND 1-5%, BASED ON THE WEIGHT OF THE CELLULOSE ACETATE BUTYRATE, OFF ATHIAZOLIDONE HAVING THE FORMULA